The present invention relates to a process for producing denitrating catalysts, and more particularly to a process for producing catalysts for use in reactions for selectively catalytically reducing nitrogen oxides with ammonia.
In recent years, much attention has been directed to measures for treating nitrogen oxides which are discharged into the atmosphere from various chemical plants, motor vehicles, etc. since such oxides are said to be responsible for photochemical smog.
Methods of removing nitrogen oxides have heretofore been proposed which include a method of catalytically reducing nitrogen oxides by using ammonia as a reducing agent. This method is thought to be advantageous in that ammonia reacts selectively with nitrogen oxides for example as represented by the following equations even if the exhaust gas contains above 1% by volume of oxygen. EQU 6NO + 4NH.sub.3 .fwdarw. 5N.sub.2 + 6H.sub.2 O EQU 6no.sub.2 + 8nh.sub.3 .fwdarw. 7n.sub.2 + 12h.sub.2 o
known catalysts used in this method are those composed of alumina, silica or like carrier and metal such as copper, iron or nickel supported by the carrier. However, because these catalysts are used in the form of particles, they have the disavantages of involving a great pressure loss, being unusable for the treatment of exhaust gases having an especially high dust concentration and necessitating a complicated replacement procedure. Catalysts comprising an active alumina carrier have another problem in that the active alumina is progressively converted to a sulfate and consequently inactivated by the sulfuric anhydride (SO.sub.3) and the like present in a very small amount in the exhaust gas.